In the broiler industry, in order to improve the productivity, researches and developments have been made for methods of breeding and rearing phyletic lines to be employed so that the body weight of broiler increases quickly and greatly. These researches and developments have resulted in remarkable improvement in body-growing speed of broiler, however, the cardiac function has not been improved so much as compared with the improved body-growing speed. A phenomenon has become to be known that a load is applied to the heart under conditions in which the amount of oxygen required by broiler increases especially in winter or at highlands, which causes cardiac insufficiency, resulting in complication of ascites.
The occurrence of ascites brings about troubles such as decrease in raising rate of broiler, and reduction in body weight increase. Such a situation has become to be considered as a problem since about 1978, and it has been a serious economic damage for the broiler industry until now.
Conventionally, in order to prevent such ascites by avoiding the increase in amount of oxygen required by broiler, several countermeasures have been adopted such that the structure of poultry house is changed, or the temperature is appropriately managed in winter. However, such countermeasures have problems that they necessitate an expensive cost and involve a large economic load.
Thus it is desired to develop an ascites-preventive agent for broilers which directly acts on broilers to prevent ascites more economically. However, no agent effective for ascites has been known.
By the way, it has been hitherto tried to add and supply quinones such as ubiquinone (also called coenzyme Q) to feeds for broilers. For example, it has been reported in British Patent Publication No. 918409 that coenzymes Q.sub.2 to Q.sub.10 are added and supplied to a feed for rearing broilers during initial five weeks of rearing in an amount of 1-100 mg/kg to improve the increase in body weight. In addition, it has been reported in Japanese Patent Laid-open Publication No. 50-82219 that a combined agent of .alpha.-tocopherol and coenzyme Q.sub.7 improves the egg laying rate.
However, any of the aforementioned reports was made prior to the recognition of ascites as a problem. They are based on the action to increase the body weight or improve the egg laying rate of broiler, but have no relation to the preventive action against ascites of broiler.
The present invention has been made from the viewpoint as described above, an object of which is to provide an agent and a feed which can effectively prevent broilers from ascites and improve the raising rate.